+/**
+ * pci_get_rom_size - obtain the actual size of the ROM image
+ * @rom: kernel virtual pointer to image of ROM
+ * @size: size of PCI window
+ * return: size of actual ROM image
+ *
+ * Determine the actual length of the ROM image.
+ * The PCI window size could be much larger than the
+ * actual image size.
+ */
+size_t pci_get_rom_size(void __iomem *rom, size_t size)
+{
+ void __iomem *image;
+ int last_image;
+
+ image = rom;
+ do {
+ void __iomem *pds;
+ /* Standard PCI ROMs start out with these bytes 55 AA */
+ if (readb(image) != 0x55)
+ break;
+ if (readb(image + 1) != 0xAA)
+ break;
+ /* get the PCI data structure and check its signature */
+ pds = image + readw(image + 24);
+ if (readb(pds) != 'P')
+ break;
+ if (readb(pds + 1) != 'C')
+ break;
+ if (readb(pds + 2) != 'I')
+ break;
+ if (readb(pds + 3) != 'R')
+ break;
+ last_image = readb(pds + 21) & 0x80;
+ /* this length is reliable */
+ image += readw(pds + 16) * 512;
+ } while (!last_image);
+
+ /* never return a size larger than the PCI resource window */
+ /* there are known ROMs that get the size wrong */
+ return min((size_t)(image - rom), size);
+}
+